Sometimes it seems that the more you learn about brewing the less you know. There are so many variables that you can’t possibly manage all of them at once.
However, there’s one thing that’s easily controlled and can alter the profile of your beer significantly: mash temperatures.
Before going any further it’s useful to take a step back and look at what’s going in the mash.
Brewers soak malt, usually made from barley, in warm water to extract sugar. This is mashing.
Malt is made by encouraging grains to start germinating before heating them to stop further growth. Malting produces enzymes capable of converting starch (inside the grain) into sugar.
Normally this conversion fuels the plant’s growth, but brewers use it to create sugary wort for fermentation into beer.
There are two types of starch in malted barley: amylose and amylopectin.
Amylose is a simple chain of glucose molecules. Amylopectin is more complicated, taking the form of tree.
Malted barley has roughly 25% amylose and 75% amylopectin. I’ll get to the significance of reducing ends and non-reducing ends later in the post.
For the enzymes to work you need to activate them. This is done in warm water.
The temperature of that water determines which enzymes are brought to life, and what they do to your wort.
There are many enzymes in malt that take part in the mash.
However, rather than cover every eventuality and lose you in detail, the two I want to explain here are alpha-amylase and beta-amylase.
By focussing on these you’ll learn a simple rule of thumb that you can use to adapt your beer to your taste, or to suit the customs of a particular style.
The first of these enzymes is alpha-amylase.
Alpha-amylase has these characteristics:
- Active between 68.5 – 70°C (155 – 158°F)
- Randomly breaks the glucose into chunks
- It can’t separate amylopectin branches
- Makes wort with high percentage of non-fermentables
The second enzyme to think about is beta-amylase.
Beta-amylase has these characteristics:
- Active between 60 – 65°C (140 – 149°F)
- Turns non-reducing end into maltose (a fermentable sugar)
- It can’t do anything with the amylopectin branches
- Makes highly fermentable worts
The important thing to realise is that changing the temperature of the mash slightly means activating a different enzyme. The difference will manifest itself in the fermentabilty of the wort.
A more fermentable wort finishes with less residual sugar and a thin, light body. Less fermentable worts produce thicker, full bodied beers with more remaining sugars.
This is useful information if you’re trying to match the target final gravity for a given style of beer.
Both are recommended reads.
Mash Temperatures Chart
Finally, I’ve condensed the above information into this simple chart:
As usual, there is always room for more complexity. Once you get used to the effects of the different enzymes you can create multi-stage mashes that take advantage of more than one of them at the same time.
But for now just think about your mash temperature next time you brew, and let me know how you get on in the comments.